It has been suggested that e.g. .beta.-carotene is effective as a prophylactic against cancerous illnesses. .beta.-Carotene as well as other carotenoids such as e.g. lycopene, bixin, zaxanthin, cryptoxanthin, lutein, canthaxanthin, astaxanthin, .beta.-apo-8'-carotenal, .beta.-apo-12'-carotenal as well as esters of hydroxy- and carboxy-containing compounds of this group, e.g. the lower alkyl esters, preferably the methyl ester and ethyl ester, have, moreover, acquired a considerable significance as colorants or color-imparting agents for foodstuffs or also as feed additives.
However, carotenoids are substances which are insoluble in water, have high melting points and, moreover, are also sensitive to heat and oxidation.
In the case of e.g. .beta.-carotene these properties, especially the water-insolubility, give rise to an extremely poor bioavailability from pharmaceutical dosage forms such as, for example, tablets, capsules etc. which contain this carotenoid. The aforementioned properties are, moreover, an obstacle to a direct use of the crystalline materials for the coloring of aqueous foodstuffs, as feed additives or also for use as a source of vitamin A, since the materials in this form are absorbed only poorly or give only a poor coloring effect. The above-mentioned properties of carotenoids are especially disadvantageous in the coloring of aqueous media, since it is extremely difficult, because of their water-insolubility, to achieve a homogeneous or sufficiently intense coloring effect.
Various processes for the manufacture of such preparations are already known from the literature, but these are associated with in each case more or less great disadvantages. Thus, for example, from German Patent No. 1 211 911 it is known to manufacture carotenoid preparations by dissolving a carotenoid in a carotenoid solvent, emulsifying the solution in an aqueous solution of a protective colloid and subsequently removing the solvent from this emulsion. The disadvantage of this process resides in the fact that chlorinated hydrocarbons are preferably used as the solvent and their removal is extremely expensive from the industrial point of view. Furthermore, for example, it is known from European Patent No. 65 193 to manufacture carotenoid preparations by dissolving a carotenoid in a non-chlorinated volatile water-miscible organic solvent at temperatures between 50.degree. and 200.degree. C. within a period of less than 10 seconds, precipitating the carotenoid in colloid-dispersed form from the solution obtained by mixing with a solution of a colloid and subsequently removing the solvent. Here also an organic solvent must therefore be removed, which again is expensive from the industrial point of view.
There accordingly exists a need for a process for the manufacture of powdered carotenoid preparations which is carried out without the use of organic solvents and which are readily dispersible in aqueous media and which, moreover, - in the case of .beta.-carotene - are suitable for the manufacture of pharmaceutical dosage forms having good bioavailability of the active substance.